U.S. Navy
Signal Flags

Even in these days of radio and
satellite communications, the U.S. Navy uses the
international alphabet flags, numeral pennants, numeral
flags, and special flags and pennants for visual
signaling. These signal flags are used to communicate
while maintaining radio silence. Navy Signalmen transmit
messages by hoisting a flag or a series of flags on a
halyard. Each side of the ship has halyards and a
"flag bag", containing a full set of signal
flags. Signals unique to the Navy are used when
communicating with other U.S. Navy or allied forces. When
communicating with all other vessels, the International
Code of Signals is used. The code/answer pennant
precedes all signals in international code.